1. Field of the Invention
The present invention relates to a semiconductor laser device used for optical disk apparatus such as a CD-R/RW drive, a DVD-RAM drive and the like, and to a method of producing the same.
2. Description of Related Art
It has been tried to increase the recording speed of optical recording apparatus, and, for example, CD-drives of 16-time speed recording have been put into practical use. In such optical recording apparatus of a high recording speed, it is necessary to momentarily start up high output laser light. As examples of lasers capable of fulfilling such required characters, there are ridge type semiconductor lasers produced by using compound semiconductors.
A semiconductor laser device is a light emitting device for inwardly reflecting light generated by recombination of electrons and holes at both of the end faces of the device, and thereby causing laser light oscillation. On both of the end faces of a semiconductor laser device, namely, a laser emission end face and a reflective end face, protective layers of alumina or the like are respectively formed for protecting the same.
However, in the process of producing a semiconductor laser device, the end faces of the device are oxidized, before the protective layers are formed, resulting in forming a number of non-radiative recombination centers on the laser emission end face and the reflective end face. At the time of laser light emission, current is injected throughout the length of the device from the laser emission end face to the reflective end face. At this time, on the laser emission end face and the reflective end face, non-radiative recombination occurs to cause heat generation. When band gap becomes small due to the heat generation, laser light absorption increases, further to cause a temperature rise. With this being repeated, so-called COD (Catastrophic Optical Damage) occurs to melt the end faces of the semiconductor laser device, so that the device is finally broken.
When the optical output of a semiconductor laser device is raised, COD occurs at a certain level (destructive optical output level). Therefore, when using a semiconductor laser device, the optical output thereof must be set lower than the destructive optical output level.